1/* 2 * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com) 3 * Licensed under the GPL 4 */ 5 6#include "linux/kernel.h" 7#include "asm/errno.h" 8#include "linux/sched.h" 9#include "linux/mm.h" 10#include "linux/spinlock.h" 11#include "linux/init.h" 12#include "linux/ptrace.h" 13#include "asm/semaphore.h" 14#include "asm/pgtable.h" 15#include "asm/pgalloc.h" 16#include "asm/tlbflush.h" 17#include "asm/a.out.h" 18#include "asm/current.h" 19#include "asm/irq.h" 20#include "sysdep/sigcontext.h" 21#include "kern_util.h" 22#include "as-layout.h" 23#include "arch.h" 24#include "kern.h" 25#include "chan_kern.h" 26#include "mconsole_kern.h" 27#include "mem.h" 28#include "mem_kern.h" 29#include "sysdep/sigcontext.h" 30#include "sysdep/ptrace.h" 31#include "os.h" 32#ifdef CONFIG_MODE_SKAS 33#include "skas.h" 34#endif 35#include "os.h" 36 37/* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */ 38int handle_page_fault(unsigned long address, unsigned long ip, 39 int is_write, int is_user, int *code_out) 40{ 41 struct mm_struct *mm = current->mm; 42 struct vm_area_struct *vma; 43 pgd_t *pgd; 44 pud_t *pud; 45 pmd_t *pmd; 46 pte_t *pte; 47 int err = -EFAULT; 48 49 *code_out = SEGV_MAPERR; 50 51 /* If the fault was during atomic operation, don't take the fault, just 52 * fail. */ 53 if (in_atomic()) 54 goto out_nosemaphore; 55 56 down_read(&mm->mmap_sem); 57 vma = find_vma(mm, address); 58 if(!vma) 59 goto out; 60 else if(vma->vm_start <= address) 61 goto good_area; 62 else if(!(vma->vm_flags & VM_GROWSDOWN)) 63 goto out; 64 else if(is_user && !ARCH_IS_STACKGROW(address)) 65 goto out; 66 else if(expand_stack(vma, address)) 67 goto out; 68 69good_area: 70 *code_out = SEGV_ACCERR; 71 if(is_write && !(vma->vm_flags & VM_WRITE)) 72 goto out; 73 74 /* Don't require VM_READ|VM_EXEC for write faults! */ 75 if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC))) 76 goto out; 77 78 do { 79survive: 80 switch (handle_mm_fault(mm, vma, address, is_write)){ 81 case VM_FAULT_MINOR: 82 current->min_flt++; 83 break; 84 case VM_FAULT_MAJOR: 85 current->maj_flt++; 86 break; 87 case VM_FAULT_SIGBUS: 88 err = -EACCES; 89 goto out; 90 case VM_FAULT_OOM: 91 err = -ENOMEM; 92 goto out_of_memory; 93 default: 94 BUG(); 95 } 96 pgd = pgd_offset(mm, address); 97 pud = pud_offset(pgd, address); 98 pmd = pmd_offset(pud, address); 99 pte = pte_offset_kernel(pmd, address); 100 } while(!pte_present(*pte)); 101 err = 0; 102 /* The below warning was added in place of 103 * pte_mkyoung(); if (is_write) pte_mkdirty(); 104 * If it's triggered, we'd see normally a hang here (a clean pte is 105 * marked read-only to emulate the dirty bit). 106 * However, the generic code can mark a PTE writable but clean on a 107 * concurrent read fault, triggering this harmlessly. So comment it out. 108 */ 109 flush_tlb_page(vma, address); 110out: 111 up_read(&mm->mmap_sem); 112out_nosemaphore: 113 return(err); 114 115/* 116 * We ran out of memory, or some other thing happened to us that made 117 * us unable to handle the page fault gracefully. 118 */ 119out_of_memory: 120 if (is_init(current)) { 121 up_read(&mm->mmap_sem); 122 yield(); 123 down_read(&mm->mmap_sem); 124 goto survive; 125 } 126 goto out; 127} 128 129static void bad_segv(struct faultinfo fi, unsigned long ip) 130{ 131 struct siginfo si; 132 133 si.si_signo = SIGSEGV; 134 si.si_code = SEGV_ACCERR; 135 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 136 current->thread.arch.faultinfo = fi; 137 force_sig_info(SIGSEGV, &si, current); 138} 139 140static void segv_handler(int sig, union uml_pt_regs *regs) 141{ 142 struct faultinfo * fi = UPT_FAULTINFO(regs); 143 144 if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){ 145 bad_segv(*fi, UPT_IP(regs)); 146 return; 147 } 148 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 149} 150 151/* 152 * We give a *copy* of the faultinfo in the regs to segv. 153 * This must be done, since nesting SEGVs could overwrite 154 * the info in the regs. A pointer to the info then would 155 * give us bad data! 156 */ 157unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 158 union uml_pt_regs *regs) 159{ 160 struct siginfo si; 161 void *catcher; 162 int err; 163 int is_write = FAULT_WRITE(fi); 164 unsigned long address = FAULT_ADDRESS(fi); 165 166 if(!is_user && (address >= start_vm) && (address < end_vm)){ 167 flush_tlb_kernel_vm(); 168 return 0; 169 } 170 else if(current->mm == NULL) { 171 show_regs(container_of(regs, struct pt_regs, regs)); 172 panic("Segfault with no mm"); 173 } 174 175 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 176 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code); 177 else { 178 err = -EFAULT; 179 /* A thread accessed NULL, we get a fault, but CR2 is invalid. 180 * This code is used in __do_copy_from_user() of TT mode. */ 181 address = 0; 182 } 183 184 catcher = current->thread.fault_catcher; 185 if(!err) 186 return 0; 187 else if(catcher != NULL){ 188 current->thread.fault_addr = (void *) address; 189 do_longjmp(catcher, 1); 190 } 191 else if(current->thread.fault_addr != NULL) 192 panic("fault_addr set but no fault catcher"); 193 else if(!is_user && arch_fixup(ip, regs)) 194 return 0; 195 196 if(!is_user) { 197 show_regs(container_of(regs, struct pt_regs, regs)); 198 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 199 address, ip); 200 } 201 202 if (err == -EACCES) { 203 si.si_signo = SIGBUS; 204 si.si_errno = 0; 205 si.si_code = BUS_ADRERR; 206 si.si_addr = (void __user *)address; 207 current->thread.arch.faultinfo = fi; 208 force_sig_info(SIGBUS, &si, current); 209 } else if (err == -ENOMEM) { 210 printk("VM: killing process %s\n", current->comm); 211 do_exit(SIGKILL); 212 } else { 213 BUG_ON(err != -EFAULT); 214 si.si_signo = SIGSEGV; 215 si.si_addr = (void __user *) address; 216 current->thread.arch.faultinfo = fi; 217 force_sig_info(SIGSEGV, &si, current); 218 } 219 return 0; 220} 221 222void relay_signal(int sig, union uml_pt_regs *regs) 223{ 224 if(arch_handle_signal(sig, regs)) 225 return; 226 227 if(!UPT_IS_USER(regs)){ 228 if(sig == SIGBUS) 229 printk("Bus error - the host /dev/shm or /tmp mount " 230 "likely just ran out of space\n"); 231 panic("Kernel mode signal %d", sig); 232 } 233 234 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs); 235 force_sig(sig, current); 236} 237 238static void bus_handler(int sig, union uml_pt_regs *regs) 239{ 240 if(current->thread.fault_catcher != NULL) 241 do_longjmp(current->thread.fault_catcher, 1); 242 else relay_signal(sig, regs); 243} 244 245static void winch(int sig, union uml_pt_regs *regs) 246{ 247 do_IRQ(WINCH_IRQ, regs); 248} 249 250const struct kern_handlers handlinfo_kern = { 251 .relay_signal = relay_signal, 252 .winch = winch, 253 .bus_handler = bus_handler, 254 .page_fault = segv_handler, 255 .sigio_handler = sigio_handler, 256 .timer_handler = timer_handler 257}; 258 259void trap_init(void) 260{ 261} 262